Diplex transmission by combined frequency-amplitude modulation



Nw. 16, 194s. c. J. YOUNG 294531,77@

l DIPLEX TRANSMISSION BY COMBINED l FREQUENCY-AMPLITUDE MODULATION Filed Nov. 29, 1943 2 Sheets-Sheet l INVENTOR. C/harle* rl' You AAAAAAAAA V VVVVVVY C. J. YOUNG DIPLEX TRANSMISSION BY COMBINED Nov. 16, 1948.

FREQUENCY-AMPLITUDE MODULATION Filed Nov. 29, B43 2 Sheets-Sheet 2 `Patented Nov. 16, 1,948;

DIPLEX TRANSMISSION BY COMBINED FRE- QUENCY-AMPLITUDE MQDULATION Charles J'. Young, Princeton, N; I., assigner to. Radio Corporation of America, a; corpration of Delaware Application November 29, 1943i, Serial No. 512,175

The present invention relates to combined' sig-- nalling systems and more particularly to a system in which sets of intelligence signals, eachv of a different kind, are transmitted concurrently".

In accordance with the present invention, facsimile signals representing a picture, object, message, or other subject matter are transmitted concurrently with signals which are to be applied to the control and operation of a printing telegraph receiver. The facsimile signals and` the printer signals are transmitted together without interference with each other and are recorded separately. The principal sets of signals, namely the facsimile signals and the printer and printer control signals, may be transmitted over a land line, cable pair, or radio link.

This result of non-interfering transmission, reception, and recording is accomplishedk in accordance with the present invention by amplitude modulating a carrier with one set. of signals and frequency modulating the same carrier at appropriate times with the other set of signals. Preferably, the facsimile signals appear as fr equency modulations of the carrier, and` the printer signals appear as amplitude modulations of the carrier. In this manner a method of modulation well suited to impressing intelligence of each kind on the carrier and to separate intelligence of both kinds from the carrier is employed.

The principal object of the present invention is to provide a method of and apparatus for` transmitting facsimile and selector signals simultaneously on a single carrier wave.

Another object of the present invention is to transmit facsimile signals and printer signals simultaneously on a single carrier wave by frequency modulating the carrier wave with the facsimile signals and amplitude modulating the carrier Wave with the printer signals.

Other objects of the invention will become apparent when the following specification and claims are read in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic represent-ation of a transmitting station of a communication system embodying the present invention;

Fig. 2 is a diagrammatic representation of a receiving station of a communication system embodying the present invention; and

Fig. 3 shows, by way of example, control circuits and printer operating circuits suitable for use With the invention.

Referring to Fig. 1 of the drawings, there is shown a facsimile scanner and modulator Ill which may comprise a scanner of any type,l for means.

example, like` that shown on page- 8,0y of Volumel of a book en-ti-tl'ed Radio Facsimilewpublished in October, 1938', by RCA Institutes Press', New York, llewI York.

A scanner of this. type, which has been` in gene eral use, provides an output. from: a photocel'l. or thelike representing tones or shades of the sub.- jectmatter to be transmitted. This` scanner output is used to frequency modulatey a carrier Wave, orexampl'e, in the manner shown and described ina patent tol Artzt, 22,321,269; grantedk June 8; 1943. A modulator of" the type shown in` this patent may bev employed in the facsimile scanner and modulator IDI.

The output from the modulator and scanner l0 is indicated graphically byv curve Hland` is 4seen to comprise a wave, the frequency ot whichfis varied in accordance with the light and dark areas of the subject matter which isbeing scanned for transmission. The frequencyi ofthe wave l'may; for example, varyfrom 33000 cycles, when White is being; scannedb to4,0(l0 cycles, when black is b eingV scanned'. The Wave l4" represents the modulated wave I4 with additional; signals appliedl in a mannerA to be later described. The output from the modulator and' scanner I0' with the additional signals. may be supplied to a, modulator and radio transmitter or carrier current transmitter i6.

In place of employing the modulator and transmitter l5, the wave Il.' may be transmitted directly over a carrier channel by connecting the Wire pair of the. carrier channel tov terminals. I8 at the transmitter and to terminals I9, (Fg.,2),. at any receiver. Communication may be had with other and perhaps more distant, receivers at the same time by employing, the modulator andv trans mitter t6 `and the carrier or radio receiver of Fig. 2.. The output from the' receiver Z0 is4 supplied to. afacsimile receiver and reeorderr't which may be of any suitable type or des-ign. The output of they carrier current or radio. receiver 2D is indicated at 23 and is substantially a replica of the Wave I1. The facsimile receiver and. recorder 22 may be of any desired type and include any desired recording apparatus. This equipment maybe arranged as shown described in detail in a patent to Koch, 2,3`l9,12 9;I gran-ted May 11, 19,431. A. limiter is preferably included s0 that a relatively small portion of the amplitude of the Wave 23; operates the facsimile; recorder. Demod.- ulation of thewave 213 may be obtained by a discriminator, a demodulatmn filter,` or any known The output trom the demodulatormay be. employed; in the.: marmer shown and described.

in the Koch patent just referred to or a chemical recorder may be used.

The facsimile transmitting scanner and recorder may be synchronized in any known inanner, for example, by the transmission of a synchronizing signal. Phasing or framing of the recorded lcopy may also be obtained in any known manner such as by transmitting a special phasing or framing signal. synchronizing and phasing may be done by varying the frequency of the carrier I4 in the intervals between the printed parts of the scanning lines.

The subcarrier frequency modulated facsimile system just described is operated so that representations of pictures or any other desired subject matter may be sent from the facsimile scanner and modulator Ill to the recorder comprised in the facsimile receiver and recorder 22.A Details of the operation ofthe facsimile system need not be reviewed as it is not part of the present invention. Application of the additional signals to the wave I4 will now be described in detail.

Reference character 26 indicates a keyboard sender or tape sender of any known type which generates five-unit selector signals suitable for operating a selective'device such as a telegraph printer. The sender 26 may be of th'e kind disclosed in a patent to Morton et al., 1,735,633, granted February 4, 1930, or it may be a complete keyboard and printer such as is shown in a patent to Noxon et al., 2,231,215, granted February 11, 1941. If the arrangement shown in the Noxon patent is used, a local printed record may be obtained on the type bar printer which is associated with the keyboard sender.

The sender 26 is shown as comprising a set of rest pulse contacts 28 and a series of five intelligence pulse contacts 29. When the sender 26 is in the standby condition, the contacts 28 are closed so that a line relay 32 is energized from a convenient power source, indicated as a battery 33. The relay circuit, which includes the sender 26, also includes a hand operated key 36 whichl is useful for signalling and may be conveniently employed in a manner to be described to start a printer at a remote receiving station or stations.

Amplitude modulation of the wave I4 with signal -combinations set up by the code contacts 29 is accomplished by the tongue and break contact 38 of the relay 32 which bridges a resistor 42 across the output of the facsimile scanner and modulator ID. Resistors 43 and 44 along with` the resistor 42 function as a pad so that, during operation of the line relay 32, the impedance reected into the scanner and the transmitter will not be much changed and frequency distortion will be avoided. The effect of the resistor 42 is indicated by the wave II, the portion of reduced amplitude occurring when the relay 32 is de-energized.

Operation of the relay 32 will produce square pulses, and 30 per cent amplitude modulation of the envelope of the wave I4 has been found to give excellent results in practice. It will be understood, however, that the degree of modulation will be varied depending upon conditions of use of the invention.

At a receiver station, the wave 23, which is a replica of the wave I1, is applied to an amplifier 49, the output of which is connected through a transformer 50 to the anodes 5I and 52 of a full wave amplitude detector 54. A detector load resistor 55 has its negative end connected to the grid 56 of a power tube 58. A condenser 51 serves as a detector filter condenser. A relay 62 in the plate circuit of the tube 58 functions as a line relay. With the detector connected as shown, the tube plate current will increase when th'e carrier amplitude decreases. The variations in current in the relay coil 62 while revised in phase correspond to the current variations in the coil of the line relay 32, and therefore the coil of this relay 62 may be the actuating magnet of a telegraph' printer such as a teletype machine. If this suggested simplified arrangement without the automatic control feature to be described is employed, the Contact 38 on relay 32 should be a make contact, or the detector connection to the grid 56 should be reversed, since printers of the usual type are idle with line current flowing. The coil of the relayv 62 also may be employed as shown to serve as a line relay to operate a signal relay 66 (Fig. 3) which in turn controls energization of the selector magnet 61 of a telegraph printer indicated generally by reference character 6B.

It is within the scope of the invention to arrange the apparatus so that the facsimile signal is transmitted as an amplitude modulation and the printer signal as a frequency modulation of the subcarrier.

By the arrangement of apparatus shown in Fig. 3 of the drawings, it is possible to operate the printer 62 automatically from the transmitting station shown on Fig. 1 over a carrier channel or radio link without the necessity of using grounded or composite circuits.

Referring now to Fig. 3 for a detailed description of th'e control apparatus, the printer 68 may be of the kind shown in Patent No. 2,231,215, above referred to, which comprises a keyboard sender T2, which may be similar in all respects to the sender 26 of' Fig. 1, and a printing mechanism (not shown) controlled by the selector magnet 6l. A motor 'I3 drives the selector and printer mechanism. Power to operate this motor is supplied from a suitable source of power 'f4 under control of a tongue and make contact 'I6 of a motor control relay 'I'I. When this relay is energized and locked in a manner to be described, the motor 'i3 will operate to drive the selector mechanism so that current pulses appearing in the magnet 61 will select characters to be printed.

A source of direct current 79 for operating the printer 68 and the relay system to be described including the line relay 62 may comprise an ordinary rectier and filter and, as shown, it may be left on continuously so that the printer equipment can be started at all times in response to a call from the key 36 of Fig. 1. One terminal of the supply source 'I9 is grounded as shown, and the other terminal is connected to a conductor 3| which serves as a bus-bar for supplying control current. The operating coil of a slow-to-operate calling relay 82 is connected to the make contact 83 of the line relay 62 over a conductor 84. rThe other terminal of the relay is connected to the bus-bar 8l. The tongue of the relay 62 is grounded.

The make contact 83 of the relay S2 is also connected to the operating coil of the signal relay 66, the other terminal of this relay being connected to the bus-bar 8l of the supply source 19. One terminal of the printer magnet 3l is grounded as shown, and the other terminal is connected through the keyboard transmitter 'I2 to the make contact 86 of the motor control relay TI. The tongue of this relay associated with the make contact 88 is connected to the break contact 815 owing through the selector magnet 61.' The slow-to-operate relay 82 will not respond to the selector signals which are current or no-current pulses of short duration. Even if for a given character, all live selector pulses in the conductor 88 are current pulses, still the relay 82 will not respond since the total time for sending a character is a fraction of a second.

'The arrangement for automatically starting the printer motor 'it will now be described. A relatively long control pulse may be obtained by depressing the key 38 shown on Fig. 1 .which will cause a long pulse to energize the relay 62 of Fig. 2. Energization oi the relay 82 for a suilicient time will cause operation of the tongue of the relay 82 and will complete a circuit from the bus-bar 8i by way of the make contact 89 of this relay, a contact stud 98 on a rotary switch 92, and through the operating winding 93 of a relay 88 to ground. Operation of the relay'QS will close the circuit of the motor control relay 'll at the make contact 98 of the relay 96.

The relay 8% is provided witha locking winding 89 which is yconnected through a third tongue and make contact |02 of the motor control relay Tl' to a tongue and make contact |04 of a slowto-release relay |86. The operating coil of the slow-to-release relay lll is connected to the make contact 89 of the slow-to-operate relay 82. The circuit of the locking coil 89 of the relay is also connected to the bus-bar 8| through a break contact E88 of the slow-to-operate relay 82. The slow-to-operate relay |06 serves as a guard to maintain the circuit or" the locking coil 99 while the tongue of the slow-to-operate relay is returning to its break contact |88.

After operation of the relay 82 upon the occurrence of a prolonged signal pulse and subsequent release oi this relay, it will be seen that energize.- tion of the motor control relay Tl is maintained since energiaation of the locking coil 99 oi the relay 88 is maintained at the break contact' |08 of the relay 82.

The rotary switch 82 referred to previously has a contact brush and a series of contact studs 8l? and ill. Alternate contact studs 9|] are connected to a conductor H2 which completes the circuit trom the make contact 89 of the relay 82 to the operating winding 93 of the relay 96. Upon each energization of the relay 82, the operating coil il@ of the switch 92 is energized which causes the ratchet pawl l! 8 connected to its core H9 to be retracted against the thrust of a compression spring |28. When the relay 82 releases, the coil H6 is de-energized and the spring |28 forces the pawlY H8 to the right as viewed in Fig. 3 oi the drawings, turning the ratchet iEl and causing the brush to move to the next succeeding contact stud 9|. This provides an arrangement for shutting down the printer t8 in response to a succeeding prolonged pulse from tl'ie transmitter station without again energizirigtlie' relay' 96:V

Assumingl that the printer 68 is in operation and that the relaysll and 96 are energized and the relay |06' is dehenergized, the brush will be on one of the lcontact studs 9| not connected to the-conductor |12 since the spring |20 will have* turned the ratchet |2| by an angular distance of one notch. 'vWhenthe next prolonged pulse `is received which will be a stopping pulse, theslow-to-operateV relay 82 will operate, breakingthe" connection ofthe locking coil 99 of the relay 98 which has been maintained at the break contact |08-, This will interrupt energization of the relay ll', stopping the printer motor 13. Since the brush lli of the'rotary switch 92 is on a blank studfSlf; the operating winding 93 of the relay 9B will notbe energized.` However, the operating winding' H8 of the rotary switch 82 will be energized", and when this winding isv cle-energized, the

brush will be stepped tothe next contact stud 88 which is connected tothe conductor ||2 in readiness for `starting the printer motor 13l in response to the `next prolonged signalling pulse. In place of the rotary switch 92 a single-pole double-throw switch may be employed having a magnet which operates the switch contact from one position to the other upon succeeding energizations.

Operation of the entire system will now be reviewed. Assuming that the facsimile scanner and modulator l0' is in operation and that the facsimile receiver Aand recorder 22 are operating over 4the radio linkprovided between the trans- 7 mitter `it? and the receiver 20, printer communication; may be initiated without disturbing this facsimile communication circuit by depressing the key 361 The key 3S need not be kept open for a long time interval, since merely depressingthe key manually for a brief time will produce a pulse which is longer than the duration of a complete five-unit selector combination. This results in de-energization of the relay 82 which bridgesv the resistor 42 across the output of the scanner and` modulator I8. At the receiving station shown in Fig. 2, this pulse is detected by the detector' 5l? and the plate4 current of the tube 58 increases causing` energization of the coilA of the relay 621.11; will lbe understood that if desired, the connection may be such that the plate current of the tube 58 will decrease upon the occurrence of a pulse, and if this isV done, a break contact on` the relay t2 may be employed as `pointed out above.

nergizatiori ofthe relay 62 will apply ground to the operatinglwinding of the relay 82 so that current willflow through thisrelay for a sufficient timeto cause it tooperate. When this relay opcrates,A the bus-bar 8| will be connected through theV tongue and front contact 89 by Way of the brush.. .aV Contact Stud 9G, and the conductor liithroughthe operating winding 93 of the relay SBtofground. This relay will operate to energize the motor controlrelay 11 starting the motor 'I3 and! closingV the printer operating circuit at' the make contact 86. The slowto-release relay |06 will operate to maintain the locking circuit on the relay 9E: through its locking coilv 99 until the relayy 8`2`` releases and maintains this locking circuitthrough-its break contact |08. Also, upon release-oiV the relay 82,` the brush will be stepped tothenext studgB which is not connected to the lconductor I2.

The printer 68 is usually provided with a cam shaft or distributor shaft which would begin to rotate when the motor 13 starts unless the shaft is held in its rest position by keeping the printer magnet 6l energized. This is accomplished through a make contact |26 on the relay |06 which keeps the printer magnet 61 energized from the bus-bar 8 during the time that the signal relay 66 is energized while the motor starting pulse is being received. This prevents the printing of garbled characters by the printer 68 during the motor starting period. When the relay |06 releases after an interval of time following its deenergization, the circuit from the bus-bar 8| is opened at the make contact |26 but in the meantime it has closed at the make contact 81 of the relay 66.

With the motor 'i3 operating, code impulses may now be sent from the sender 26. Briefly, if this sender is of the type which operates from a keyboard, when a key lever on the keyboard is depressed, the contacts 28 are first opened, initiating a start pulse indicated by reference character |28 on Fig. 3 of the drawings. The cam shaft (not shown) of the sender 26 operates the code pulse contacts 29 in succession to a marking or spacing position to give successive pulses of the ve unit code in a well known manner. These pulses |29, shown in Fig. 3 of the drawings, are numbered l to 5. When transmission of these live pulses has been completed, the contacts 28 again close, giving the rest condition |30 which is maintained until the next key lever is depressed or the next operation of the tape sender occurs in the event that a tape sender is employed. These pulses originating in the sender 26 are repeated by the relay 32 and are detected at the receiving station by the detector 54 and are also repeated by the relay 62. The signalling relay 66 also repeats these pulses, and since the printer 68 is or may be of the type which operates upon current interruption, that is as previously explained, marking pulses being no-current pulses, these pulses will appear as .indicated by reference character |33 so that the start pulse will correspond to an energization of the relay 66 which produces a current interruption at its make contact 31.v

The printer will respond to these signals for as long as the sender 26 may be operated.

When the operator at the sending station of Fig. 1 has completed transmission, he will depress the key 36 thereby providing a pulse similar to the motor control pulse indicated by reference character |38 on Fig. 3 of the drawings. As previously explained, upon occurrence of this pulse, the relay 82 will operate breaking the circuit of the locking winding 99 of the relay 96 and also, the brush will be stepped to the next stud 90 which is connected to the conductor ||2.

The printer channel which has been described in detail may be utilized for indicating to an operator at a receiving station that facsimile cornmunication isv desired. For example, the facsimile scanner and modulator I0 may be placed in operation to transmit an unmodulated wave I4 which will be received by the detector 54. If now the key 36 is depressed, the printer 68 at the receiving station will be placed in operation. The keyboard sender 26 may be manipulated to apprise the receiving operator that facsimile communication is desired and the operator will then start his facsimile reproducer and receiver 22.

The operator at the transmitting station may then depress the key 36 to stop the printer 68 which is no longer needed and place copy for transmission in the facsimile scanner and modulator l0.

If this suggested mode of operation is followed, it will be necessary at all receiver stations to keep the carrier current or radio receiver 20 in operation at all times which may be done with slight expense, since such a receiver, being of a simple nature, will operate with expenditure of very little power.

The relay 82 may be used to control other apparatus than a printer, and the relay 66 may be used for other purposes than operating a selector of a printer. Other uses for these relays will suggest themselves to those skilled in the art and such other uses come within the scope of the present invention.

Various modifications of the system shown and described herein by way of example are possible, without departing from the spirit and scope of the invention described herein, and it is desired that any and all of such modifications be considered within the purview of the present invention defined by the hereinafter appended claims.

Having now described the invention, what is claimed as new and desired to have protected by Letters Patent is:

1. A control signal receiving system comprising means to recover control signals from a carrier modulated with image signals and control signals, a relay responsive to prolonged signals recovered from the carrier, another relay responsive to prolonged signals and also signals having a shorter time dura-tion, a control circuit connected to the contacts of said rst named relay, a control circuit connected to the contacts of said second named relay, said lirst named control circuit being operative to exercise a control function upon operation of said rst named relay, and said second named circuit being operative upon operation I, of said second named relay to exercise a further control function, and means for preventing functioning of said second named circuit when said first named relay operates initially.

2. A facsimile signal receiving system comprising means to recover facsimile image signals, other intelligence signals and control signals from a carrier, a relay responsive to control signals, another relay responsive to control signals and said other intelligence signals, a control circuit connected to the contacts of said rst named relay, an intelligence translating circuit connected to the contacts of said second named relay, said control circuit being operative to exercise a control function in response to a control signal, said intelligence translating circuit being operative also in response to control signals, and means for preventing operation of said intelligence translating circuit when said first named relay operates initially.

CHARLES J. YOUNG.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,712,528 Swezey May 14, 1929 2,075,071 Usselrnan Mar. 30, 1937 2,103,847 Hansell Dec. 28, 1937 2,289,157 Whitaker July'?, 1942 2,332,645 Keithley et al Oct. 26, 1943 

